Which statement does not apply to foil-type sensors?

Foil-type sensors are designed to detect physical intrusion or tampering by detecting a break in the sensor's foil material. These sensors function as a psychological deterrent for potential intruders, since their presence suggests a security measure is in place, making them reconsider their intentions.

Regarding the cost of installation, while it may not be the most expensive option available, the term "cheap" can be subjective as it depends on various factors, including installation environment and specific requirements of the security system. However, option A is indicative of a broader misconception about these sensors; they can sometimes require more careful installation measures depending on the environment, which can increase costs rather than decrease them.

Foil-type sensors are also known for being sensitive to false alarms. For instance, they can register false positives if there are incidental breaks in the foil that are not related to unauthorized activity. This characteristic highlights the importance of careful placement and environment consideration when employing these sensors.

In summary, while foil-type sensors have cost benefits, they do not universally qualify as "cheap" regarding installation, particularly when one takes into account the potential for additional expenses based on installation needs and equipment requirements.